Heat transfer plate construction



March 5, 1963 H KUEHL 3,079,994

HEAT TRANSFER PLATE CONSTRUCTION 'Filed Jan. 25. 1957 ATTORNEYS Unite States Y.

3,079,994 IEAT TRANSFER PLATE CONSTRUCTON Heinrich Kiiehl, Stuttgart, Germany, assigner to Daimler- Benz Aktiengesellschaft, Stuttgart-Unterturkheim,

Germany Filed Jan. 25, 1957, Ser. No. 636,278 Claims priority, application Germany Jan. 30, 1956 4 Claims. (Cl. 16S- 166) The present invention relates to heat exchangers which consist of parallel plates, the intermediate spaces of which are alternately traversed, preferably in crossor counterow pattern, by the media which are to be heated or cooled.

In the prior art heat exchangers consisting of a plurality of plates are known in which corrugated sheet metal members are arranged between the plates, so that channels in the direction of flow are formed between the sheet metal members and the plates through which the media may flow.

The present invention aims at a particularly favorable construction of such plate heat exchangers, i.e., heat exchangers formed by a plurality of plates which enables a construction of heat exchangers which are relatively small and therewith relatively inexpensive, of light weight, and space saving with simultaneous relatively high eiciency.

It is proposed, according to the present invention, that the channel walls formed by the corrugated sheet metal members be provided with interruptions or discontinuities :in the direction of flow at least within those regions in which the channel walls do not abut against the plates. In that manner, the hea-t transfer is considerably increased as compared to heat exchangers having channels which are uninterrupted or continuous. This is due to the fact that the heat transfer is proportional to the tempera-ture gradients along the wall. This temperature gradient is relatively steep at the beginning of the entrance or admission of a flow into a channel as at rst all of the streamlines have the same temperature. However, in the course of flow through the channel the streamlines located in proximity of the walls cool off or heat up until an equilibrium condition is obtained in which the maximum temperature difference with respect to the wall is located in the center of the channel and decreases towards the sides relatively gradually. If the channel walls in accordance with the present invention are interrupted over and over again, then the flow with each interruption is repeatedly disturbed by the formation of turbulences, eddies or the like, i.e., the temperature is thereby again evened out over the entire cross section of flow so that the temperature gradient in proximity to the wall during the entrance into the next channel portion is again very great.

In that manner, it is possible to obtain the relatively high heat transfer over the entire length of ow through the heat exchanger which is present only with a simple continuous uninterrupted tube or pipe only directly at the entrance thereof.

A simple manufacture and construction including the desired interruptions is possible if the corrugated sheet metal members consist of many strips made of sheet metal which are disposed transversely to the direction of ow and at a distance from each other. On the other hand, it is also possible to manufacture a plate heat exchanger in accordance with the present invention in such a manner that the corrugated sheet metal members consist each of a uniform piece of sheet metal which is provided with recesses or openings which correspond to the desired interruptions. In that manner, an accurate mutual position of the partial channels is assured.

If, in accordance with a further feature of the present 3,G'19,i94 Patented Mar. 5, 1953 invention the channel pieces which are separated from each other by the interruptions are disposed transversely to the direction of ow, then it is possible to achieve with still greater certainty a disturbance of the temperature prole present at the end of cach individual channel piece and may thereby also decrease the distance of the individual strips in the direction of flow.

According to a further feature of the present invention, a special construction or enclosure may be provided with plate heat exchangers in which the two media are at different pressures so as to absorb the pressure forces tending to force apart the limit or boundary plates of the high pressure parts, for example, in the shape of particularly strong terminal plates or terminal plates provided with ribs. In that manner, the channel walls arranged between the boundary plates of the high pressure portions are relieved to a large extent from the tensile stresses ordinarily required thereof for keeping together the boundary plates or may be relieved altogether from such ensile stresses. This is particularly advantageous in connection with a construction according to the present invention having sheet metal members provided with interruptions, as in such a construction, by reason of the interruptions, the connecting surfaces between the sheet metal members and the plates are also interrupted and such connections, for example, eifected by soldering or brazing, from an over-al1 point of view cannot absorb as much tensile stress as with a connection with uninterrupted sheet metal members.

Furthermore, in connection with heat exchangers for media of different pressures, it is proposed in accordance with the present invention that the shape of the corrugations of the sheet metal members for the medium at lower pressure be provided with essentially rectilinear reinforcements or supports from plate to plate and that the shape of corrugations of the sheet metal member for the media which are under higher pressure be provided with essentially S-shaped, curved connections from plate to plate. In this manner, it is prevented to a large extent that the spaces which are subjected to lower pressure are squeezed together due to the forces produced thereby. On the other hand, if a limited movement of the boundary plates should take place in this sense, i.e., in the direction of compressing the low pressure spaces by a ready increase in the distance of the plates from each other which define the space for the higher pressure, then the corrugated sheet metal members of the high pressure space do not become detached from the boundary plates as they are sufficiently elastic as a result of the S-shaped curvature to follow this increase in distance.`

For purposes of decreasing the losses in ow, the channel walls may be provided with rounded off end sides or with streamlined profiles as visualized in cross sections parallel to the plates. Furthermore, in those cases in which clogging up of the heat exchanger is feared by reason of foreign bodies being carried by the flow medium, the present invention proposes to let the cross sections of the flow channels of the individual channel pieces deviate from each other, preferably in such a man ner that the channel pieces located at the entrance of the flowing medium into the heat exchanger have a larger cross sectional area.

Accordingly, -it is an object of the present invention to provide a heat exchanger which offers a very favorable construction with the use of plates.

Another object of the present invention is to provide an extremely eiiicient heat exchanger which is, nevertheless, compact and sturdy, and has considerable space sav-v ing characteristics.

A primary object of the present invention resides in the provision of a heat exchanger which increases the eiciency thereof to a very considerable extent.

aereas@ Another object of the present invention resides in the provision of a heat exchanger which increases the heat transfer capacity for a given size by simple and inexpensive means.

' Still another object of the present invention resides in the 'construction of av heat exchanger which is designed to continuously disturb theow'lines so as to even'out and rtherewith increase the eective temperature gradient throughout the system.

A still further object ofthe present invention is the provision of a heat exchanger which is 'soconstructed as to even out temperature distribution over the entire cross section'throughout the entire' ow path thereby Vassuring,

a m' vimumheat transfer overY the entirelength of the flow of( the medium throughfthe heat exchanger;

still further object of the present inventionis the Y provision of 'aheat exchanger which, contraryftoknown,v

devices, provides' efcient heatv transfer o ver the entire length thereof insteador 'only at the entran'ce. as isfthey case with most present day known heat exchangers.

"A stillg'further object of' the present inventionresides in; the provisionof such aheat exchanger which,fulfillsv alljt'he aforementionedobj'ectsina manner which lends itself readily'V to inexpensive manufacture" 'i Another object of the present invention isto provide a constructioufor a heat'. exchangerwhich readily resists any forcesdu'e to differences infr pressure bctweenjthe mediav within the heat exchanger.'

yOther objectsjof thepresent` invention reside in the,

provision of a heart exchanger which minimizes ilow losses byllthe construction of the end portions oflthe channelsr and whichV also lessensthe dangerofclogging'up by the presence of foreign particles which may be carried through this system by the `media. i

V'hesefand other objects, features and advantages of.

the present invention willV become morey obvious from the following 'description when taken in connection with the` accompanying drawingwhich shows, for purposes of illustration only, three embodiments in accordance with the present invention, and wherein:v

FIGURE 1 is a perspective View of a first embodimentgofwa heat exchanger in accordance with the present,v

embodiment of aplateheat exchanger in accordance with the present invention for use with the counter flow principle in' which media of different pressure are to be used.

VReferring now to the drawing wherein like reference numerals are used throughoutthe various views to designate'like parts, and more particularly to FIGURE 1, reference numerals 1010 14 designate the plates which separate from'ea'ch other the spaces for the media which arein mutual heat transfer relationship within the heat exchanger and/which flow through the flow channels ac-I cording to the cross-flow principle. An appropriately largenumber ofvindividual sharp-edged undulated or corrugated `individual sheet metal strips generally designated by reference numerals 1S Yand '16' form the channelstor the first medium owing from the right to the left or vice versa, whereas individual sheet metal strips generally designated 17 and 18 form the channels for the second medium flowing at essentially'right angles to the 'directionfofrlow of the first medium. The strips ISL-18 areY formed from'separate`at sheet metal strips hat/ inge width corresponding to the desired, predetermiiicdY length of each channel portion and Vmay beshaped to'asisu'me the configuration shown inthe drawing in anyv suitable manner.

As shown in FIGURE 1, each of the sheet metal strips 15 is formed so as vto have at portions 15a and 15by b'y means of which they are secured to the plates 10 and 11, respectively. The flat portions 15a and 15b are joined by essentially rectilinear portions 15a and 15d thereby giving the eiect of undulated orqcorrugated sheetv metal strips, The sheetmetal strips 1 6, l17 r and 18 are each provided Vwith.corresponding portions 16a, 16b, 16C and 16d; 17a, 17b, 17C and 17d; and 1q, 18 b, 18c and 18d, respectively.

FGURE 2 showsv a llatAv sheet metalmember generally` designated by reference numeral YA31 'provided with appropriately shaped recesses 19tl The sheet metalsmember S1 may bef used toconstr'uct anv arrangementcorre;A

spending to" the ,individualstripsfo sheet metalmembers,

15,'1'6i17or18 shown inQFIGUREhl. This may.. b odo folding the sheet metal 'member 31 about lines 20,1, 20a, Ztb, 26e, 20d, 20e, 201, 20g, 29h, et ceteraashown in dot-and-dash lines in'FIGUREQ, soJt'ha't, example# the' portions located between 20c `and 20d, and betweenV 2tlgv and 20h correspondQtofthe flat portionslror 15b;v

portionsthereof will constituteY the other corresponding., remises .thereof- The bending or, shapingE creationist the. Sheet. rtl/stal: member 31 kmaybe done inany1 suitable.manner. Ittis; understood thatinsfead of providing.,consslratignsuh; as'vshown in FIGURE 1, the sheet metal memberv may also vbe shapedin any other suitable manner. so as to pro, Vide, fory example, corrugations essentially in the shape of;`VV

those designated by referencenymeral -26 in FIGURE3. FGURES shows-across section .through still another1 'embodiment of a plate heat exchanger in arxgorclance` with the present invention in which, in addition to vthe heat ex?, change pilatesfltl-li two terminal securing plates 21-a1 1 d Z2 are provided, The gas streams flow, in that. embodig j ment according tothe counter-flow principle1 as is indicated by the symbols of the point and tail ofr an arrow indicated in the drawing whereby the symbols523 indicate the point of the arrow, i.e., the How in the direction to ward the viewerwhereas the sym-bol 24 indicates thetail however, is to be VpreventedV to a large extent bythe recti,-

linear leg portions or supports 25, then the S-sbapedbent lsheet metal strips 26 do not tear ott from the heat exchange plates lil-13 to which they are secured in any,

sui-table manner as by soldering orbrazing, as the S-shape assures sufficient elasticity for a yielding in the.direction` of tensiorn As shown in FIGURE 3, the walls of each strip-26 areY so constructed as to include at parts and reverselyVV curved portions, thercurv-a-ture of one of these portions merging with thel curvature of the other, These reversely curved vportions areI disposed intermediate of flat parts, the latter beingparallel toandsecured to respective pairs Vof Yadjacent heat exchange plates 10,-13; shown in this,

figure. These' reversely curved portions are thus free of direct connectionf to these plates and provide the elas ticity just referred to, since theishape enables them to yield under the influence of the high pressure ow 23;v

While VI have shown and described seyeral preferred embodiments in accordance with thepresent invention,

it is .understoodtthat the same is not limited thereto but is susceptible ofmany changes and modifications Vin accordance with the present invention, and I intend to cover y of plates comprising a rst set of adjacent plates defining iirst spaces intermediate each pair of said adjacent plates, said plurality of plates further comprising a second set of adjacent plates defining second spaces in-termediate 'each pair of said last-named plates, said plurality of plates including at least one plate common to said first set and to -said second set, said tirst spaces `being adapted for flow therethrough of a high-pressure medi-um, said second spaces being adapted for flow therethrough of a low-pressure medium, said heat exchanger further comprising first undulated sheet metal strips in said rst spaces having flat portions secured to said first-named adjacent plates and forming a plurality of channels in the direction of ow of said high pressure medium, said strips being spaced -from each other in the said direction of ow of said high pressure medium, said heat exchanger further comprising second undulated sheet metal lstrips in said second spaces secured to said `adjacent plates of said second set, said second undulated sheet metal strips -forming a plurality of channels in the direction of ow of said low pressure medium, said second undulated sheet metal strips being spaced from each other in said direction of ow of said low pressure medium, said iirst set of adjacent plates being subject to movement relativ-e to each other in response to pressure of said high pressure medium, said rst undulated metal strips comprising means adapted for yielding movement in lresponse to said movement of said iirst set of yadjacent plates, said means adapted for yielding movement comprising reversely curved portions of said undulated strips, said yreversely curved portions being intermediate said at portions and being 'effective-to relieve said tiat portions ytrom strains tending to separate said flat por-tions from said first-named adjacent plates.

2. A plate-type heat -exchanger according to claim 1, wherein said reverselycurved portions are free of direct connection to said iirst set of `adjacent plates.

3. A pl-ate-type heat exchanger :according to claim 1, wherein said second undulated sheet metal strips comprise rectilinear leg portions extending between each pair of lsaid second set of adjacent plates.

4. A plate-type heat exchanger according to claim 1, wherein said first-named plurality of channels and said second-named plurality of channels extend in the same general direction.

References Cited in the tile of this patent UNITED STATES PATENTS 2,360,123 Gerstung etal Oct. 10, 1944 2,429,508 Belaie Oct. 21, 1947 2,571,631 Trumpler Oct. 16, 1951 2,595,457 Holm et al. May 6, 1952 2,656,158 Hodson et al Oct. 20, 1953 2,912,749 Bauernfeind et al Nov. 17, 1959 FOREIGN PATENTS 23,356 France June 14, 1921 (Addition to No. 516,802)

506,396 Canada Oct. 12, 1954 631,300 Great Britain Oct. 31, 1949 882,208 France Feb. 22, 1943 

1. A PLATE TYPE HEAT EXCHANGER COMPRISING A PLURALITY OF PLATES COMPRISING A FIRST SET OF ADJACENT PLATES DEFINING FIRST SPACES INTERMEDIATE EACH PAIR OF SAID ADJACENT PLATES, SAID PLURALITY OF PLATES FURTHER COMPRISING A SECOND SET OF ADJACENT PLATES DEFINING SECOND SPACES INTERMEDIATE EACH PAIR OF SAID LAST-NAMED PLATES, SAID PLURALITY OF PLATES INCLUDING AT LEAST ONE PLATE COMMON TO SAID FIRST SET AND TO SAID SECOND SET, SAID FIRST SPACES BEING ADAPTED FOR FLOW THERETHROUGH OF A HIGH-PRESSURE MEDIUM, SAID SECOND SPACES BEING ADAPTED FOR FLOW THERETHROUGH OF A LOW-PRESSURE MEDIUM, SAID HEAT EXCHANGER FURTHER COMPRISING FIRST UNDULATED SHEET METAL STRIPS IN SAID FIRST SPACES HAVING FLAT PORTIONS SECURED TO SAID FIRST-NAMED ADJACENT PLATES AND FORMING A PLURALITY OF CHANNELS IN THE DIRECTION OF FLOW OF SAID HIGH PRESSURE MEDIUM, SAID STRIPS BEING SPACED FROM EACH OTHER IN THE SAID DIRECTION OF FLOW OF SAID HIGH PRESSURE MEDIUM, SAID HEAT EXCHANGER FURTHER COMPRISING SECOND UNDULATED SHEET METAL STRIPS IN SAID SECOND SPACES SECURED TO SAID ADJACENT PLATES OF SAID SECOND SET, SAID SEC- 